A need has long been recognized to sense the torque loads transmitted by rotating machinery, especially machinery used in relatively low speed, high torque applications such as winches, gearboxes, swingdrives and the like. Often, the purpose of sensing the torque load is safety related, e.g., to prevent the overloading of some component of the equipment. For example, swingdrives are used on vehicles to horizontally rotate booms, platforms and the like. Overloads may be caused by swinging the boom when the vehicle is on sloped terrain, by striking an object to the side of the vehicle while articulating the boom, and when the boom, while extended to the side of the vehicle, is used to pull a load, either by forward movement of the vehicle or by continued articulation of the boom. By sensing the torque loads transmitted through the swingdrive or other machinery, loads on the boom can be monitored, either manually, i.e., by the operator, or automatically, i.e., by control equipment.
Various torque sensors for rotating machinery have been developed. Many of these sensors are made for laboratory use or precision measurements, and are not rugged enough to handle the full load of a heavy industrial gearbox. Other sensors use electrical brushes, electrical slip rings, radio frequency (RF) transmitters and the like to measure and indicate the torque being transmitted. Such component tend to be wear- or damage-prone when used in dirty, dusty, harsh environments often encountered by heavy equipment like winches or swing drives. Still other torque sensors have been made for specialized gearbox types, e.g., worm-gear drives, but are not readily adaptable to other gearbox types, e.g., planetary gear drives.
A need therefore exists, for a torque sensor that is rugged and well suited for use in heavy mechanical equipment such as hydraulic swingdrives, and further that is suited for use in different types of drives, including planetary gear drives.